Zugvogel IIIa

[mlachow]

Zugvogel IIIa

Wingspan 4.05m

Length 1.7m

Weight 3.8Kg

Root chord 288mm

Designer - Chris Williams

Web Site - Original Build Thread https://scalesoaring.co.uk/phpBB3/vi...hp?f=12&t=2967

Main Wings - Two Piece

Main Wing Materials - Balsa / Ply / Spruce / Steel Joiner

Airfoil HQ35/14-12.

Fuselage Single piece, high wing, single wheel of Balsa, Ply, Spruce

Tail Removable stab, Balsa, Ply

Control Surfaces Ailerons(2), Spoilers (2) Rudder, Elevators, Tow Release.

Other References. https://www.ig-scheibe-flugzeuge.de/...01-01-2021.pdf

Merry Christmas, new build thread now that I have completed making the kit.

[lenb]

You're a building machine Mike.

[mlachow]

Actually, Chris WIlliams is a building machine. He cranks out the plans plus builds at least 3 models a year from what I can tell in scalesoaring.co.uk forums.

[mlachow]

I made a few more parts on the router. I made a bunch of gussets for the wing TE. That will save a little time cutting things up. I also confirmed that I had the correct canopy for the model. If you look in the picture you can see the raw canopy that you start out with. It is almost as large as the whole front of the fuselage. It will be cut down to just a small little piece in the end.

You can also read the articles Chis did for the Scheibe-Loravia Topaze. It is very similar in construction. Scheibe-Loravia Topaze 1:4.2-Scale | by Chris Williams | The NEW R/C Soaring Digest | Nov, 2021 | Medium, Scheibe-Loravia Topaze 1:4.2-Scale | by Chris Williams | The NEW R/C Soaring Digest | Dec, 2021 | Medium

[mlachow]

All the parts so far have been cut with my Shapeoko 4 XL. The nice part about the PDF files of the plans is they are vector PDF's and not bitmaps of a scanned plan. With this kind of PDF you can do some conversions of the PDF into files suitable for the programs for the router. I converted the plans into SVG files using an online converter. But there is still more work to do. I had to clean up many of the parts since the vectors data from the PDF files is not perfect CAD data. For the best cutting program, I need to make sure that the rib or former or whatever part is one closed curve. The fuselage formers with all the notches were the messiest pieces. I needed to adjust some points to connect all the little lines and curves from the PDF conversion. On the stringers, the best thing to do was add a little straight-line segment to make one continuous outside curve and also redraw the notch for the stringer. I used the Carbide Create program that is supplied with the machine to do this 2D drawing and then generate tool paths and add tabs to hold parts to the sheet. It took about two weeks to do most of the cutting. I did have to wait for some more plywood to finish things up.

Most of the cutting was done with a 1/16 bit so there was a minimum of dust between the small cut and the dust collector. The thinnest ply worked best leaving full depth tabs to hold the parts. I haven't done a vacuum hold down yet. I clamped all the sheets along the edge with a long clamp I made out of plywood. Thicker ply I cut leaving a thin tab in places. On thinner balsa I tried to keep most tabs on the end grain so they could be small in size. On the thicker balsa pieces, I left an onion skin around the outline to hold the part.

The conversion went well. I had three minor errors I found when checking the parts to the plans and I recut the stab TE piece when it bowed after being cut from stresses in the sheet of wood. You do get to really study the plans cutting out the parts this way. It is also results in less dust to clean up.



I needed a bunch of angle pieces for the fuselage jig. I cut those on a portable bandsaw. For the holes, I clamped the pieces to a block and kept drilling with the CNC router.

[mlachow]

I attached all the building supports for the fuselage to the aluminum angle pieces. I also made some of the 6mm ply pieces out of 3mm ply. Those are glued up and the F7, F7a formers are laminated together.

This is just a secondary building project right now. I am restoring an old MG-2 old-timer right now. (1/2a size version) So far the wing covering has been replaced. The fuselage needs a modern radio install now.

[mlachow]

I have been fitting the fuselage formers and tweaking the fixture for building the fuselage. Nothing has been glued yet. Fortunately I had a two pieces of spruce long enough for the full length of the fuselage.


I had to resolve some minor issues with the rear of the fuselage. there are some minor issues on the plans for station locations and this was resolved by just making spacers to line up everything. The rear formers are all equally spaced.



I have a good idea how all the parts fit now. One last check for alignment and I can start gluing things.

Something must be wrong, I didn't build the rudder first.

[mlachow]

Chris Williams has been helpful in explaining any confusing details on the plans. The plans are 2D drafting done in a CAD program. They are not generated form a full 3D model. As a result there are some minor issues that pop up. This also explains why I had a bit of rework on the PDF conversions to get all the edges to meet. The CNC toolpath is much easier to generate when you have a continuous edge. The effort to test fit all the fuselage parts helped. Making some spacers helped set the rear formers properly. Since they are evenly spaced, I also found that the P6 part on the top of the fuselage was 1mm short. I still ended up with some issues with F4. Either the part is not wide enough, or I didn't place it properly. They keel pieces do not lock the position of all the formers. I marked the keel parts partly from the plans. The K3 part behind the wheel is the one without a good reference point.

[mlachow]

One last thing to do before starting to glue. The F7 former has an aluminum bracket that is part of the wing joiner mount. I drilled and bolted the plate to the former, spacing it 3mm below the top of the former.

I started gluing the front end. The first 5 formers and two keel pieces along with the main longerons. I was lucky to have a few really long spruce strips to make the this without any splices.



Next is gluing the mid-section formers. This was done in steps. I started gluing the keel and longerons as well as the top ply plate. The second step was gluing in the landing gear mount plywood.


The top ply parts P1 and P3 were added. These need to be clamped and P2 can be added after they cure. This is all ply and spruce and everything is glued with epoxy.

[mlachow]

P2 can be added. The strips at the top of the cockpit opening are also added.



There are some partial longerons in the mid-section that are added next. They stop mid-air behind the wing. They still need to be camfered so that they blend in with the covering.


The real fuselage has a fiberglass front section and fabric covered welded tube frame for the rest. At this point the construction has mostly been for the welded frame part. The front formers are really just placeholders that will eventually be ripped out after creating the "fiberglass" front end by sheeting the front with 1.5mm ply and covering that with fiberglass.

[mlachow]

Time to progress to the back end of the fuselage. I cut some ply spacers to align and space all the rear formers. Stating from the wing and working backward, the formers were glued to the side and bottom longerons.


Two more longerons are added left near the top of the formers. Once those are added, it is time to fit the diagonal hard balsa pieces.to the frame. There are some ply pieces that fit between the top longerons, P4-P8. That leaves the back end ready for adding the fin and stab mount. That will wait until the tails are built. in case any adjustments are needed.

[mlachow]

Next up is sheeting the front end. It is done with 1.5mm (1/16) plywood. It is an oval cross section, so this is a compound curve. The number of strips is reduced by making some wider ply tapered pieces and scoring and cracking the middle ply a little to curve each piece. I generated my own planking strips by calculating the circumference of each station. You can find calculators for almost anything on the Internet. I divided it up so that the front end was small enough to work around the front bulkhead. It is divided up to around 20 pieces around the outside. I used the length at each former to generate a strip curved on both edges. Then I cut out a bunch of strips. Some long ones for the bottom and some shorter ones for the top of the nose. I made one slightly larger piece for the cockpit area. The part behind the cockpit does not have the same bend radius as the nose.



I started sheeting the cockpit area. This is only one piece with one notch cut in it.

[mlachow]

Continue applying sheeting to the top of the nose. I got lucky and three strips each side fit with just a little trimming along the center. You can see the individual strips and the cut line down the middle of each piece. I mixed a little milled fiberglass in the epoxy for the joint at the cockpit area. Fit, glue, wait a few hours, repeat. I won't be able to do three pieces at a time on the lower part of the fuselage. I will do a little sanding on the plywood, then apply filler to the plywood. I will some of the West systems fillers with epoxy. I don't want to use autobody filler in the middle of winter. The machine cut planking pieces sure saved a lot of time fitting pieces.

[mlachow]

The front planking is almost complete. There are probably four strips remaining on the bottom.



The front end looks pretty good. It's time to do the first coat of filler. West 410 microlight is wonderful stuff. I mixed up some like creamy peanut butter and then spread this over the planking. One of my favorite building tools are the room key cards from hotels. They make great disposable squeegees and bend nicely to shape.

[mlachow]

Next up is the fin and rudder. I need the fin to finish gluing the last former at the rear. The rudder post is glued to that former. It is simple construction, rudder post, ribs, and sub-leading edge get glued together. Then it is sheeted with thin plywood. The plans call for 0.6mm ply but that can't be found in the US easily. So, it is either 0.4 or 0.8mm, 1/64th or 1/32. It is not that large, and the sheeting extends back to cover the hinge line gap. I went with some 1/32 and sanded both sides before gluing it on. I used the iron-on technique to attach the sheeting. Precoat the contact areas of the sheeting and the fin with aliphatic. Let it dry. Then attach it by heating up the glue with a covering iron. The LE glued-on front and tip block finish the fin. It is also predrilled for the hinges

The rudder needed some "review". All the ribs are fine on the plans. But the side view does not have R6 and R7 in the correct location. I had used that originally to cut my rudder LE. And I cut it out of slightly thicker 1/4 balsa so I could put in slots for the ribs. I ended up cutting a new rudder with the corrected spacing. The TE has 1.5mm sprue and some additional 3mm balsa laminated to the spruce. The strip fits in a notch in the ribs. It easily builds vertically and easy to check that it is straight. The final detail is adding the gussets at the rudder TE. I precut the shapes from 1/32 ply and used some small chisels and a knife to fit them to the ribs.

[mlachow]

The fuselage still has assorted little pieces to add. Some balsa fillers are needed in the wing mount area. At least this keeps a few bits of balsa scrap from hitting the trash.



The stab is built next. It is just a simple balsa frame with ribs and a sub leading edge. The center is filled with balsa. It will have a bolt through it to hold it down. Some spacers were used to keep things straight when gluing the LE and TE. The plans had a 5mm TE and I used 1/4 balsa and created notches to align the rib spacing. The sheeting is a firm piece of 1/16 balsa. The sheeting was ironed on the first side,



Flip it over, and finish the infill of the balsa in the center. This is the top side so there is some 1/32 ply just under the surface in the bolt area. Some extra balsa was added for the hinge points. The second side of the sheeting will be glued normally and blocked up on some precut fixtures to hold the stab in alignment. The sheeting overlaps the TE to cover the hinge line gap.